1. Field of the Invention
The present invention relates to a bladder-type accumulator.
2. Description of the Relevant Art
Fluid circuits such as hydraulic pressure circuits, for example, employ an accumulator as an auxiliary hydraulic pressure source for accumulating a fluid such as working oil under pressure. Such an accumulator generally comprises a hollow housing with its interior space being divided into a back pressure chamber and a reservoir chamber by a bladder made of a flexible material such as rubber. The back pressure chamber is filled with a nitrogen gas under high pressure, and the oil is stored under pressure in the reservoir chamber. The bladder has its periphery pressed against the inner wall surface of the housing by an annular holder, hermetically sealing the back pressure chamber and the reservoir chamber from each other.
However, the accumulator of the above type is disadvantageous that the nitrogen gas filled under high pressure in the back pressure chamber may leak through the pressed region where the bladder is pressed against the inner wall surface of the housing or the bladder is held by the holder, into the reservoir chamber where the nitrogen gas may dissolve into the oil in the reservoir chamber. Especially if the bladder is made of rubber, the nitrogen gas filled under high pressure in the back pressure chamber is inevitably permeated through the bladder and dissolved into the oil in the reservoir chamber. When such permeation leakage occurs at the same time the leakage through the pressed region, the performance of the accumulator is impaired.